Changes in Soil Microbial Communities Associated with Pinus densiflora and Larix kaempferi Seedlings under Extreme Warming and Precipitation Manipulation

Soil microbial communities are essential to the terrestrial ecosystem processes by mediating nutrient cycling, and their function and composition may be altered under climate change. In this study, the effects of extreme climate events (extreme warming and precipitation pattern) on the microbial communities and extracellular enzyme activities in the soils planted with 1-year-old Pinus densiflora and Larix kaempferi seedlings were investigated. Open-field warming (+3 °C and +6 °C) and precipitation manipulation including drought induced by the complete interception of rainfall and heavy rainfall (113 mm per day) were applied from 13 July to 20 August 2020. The activities of soil enzymes, including β-glucosidase, acid phosphatase, N-acetyl-glucosaminidase, and leucine aminopeptidase, microbial biomass carbon and nitrogen, and changes in microbial community composition were determined. The microbial biomass carbon was 15.26% higher in Larix kaempferi-planted soils than in Pinus densiflora-planted soils. Fungal Chao 1 in the heavy rainfall and drought plots were 53.86% and 0.84% lower than the precipitation control, respectively, and 49.32% higher in the Larix kaempferi plots than under the Pinus densiflora. The fungal Shannon index was 46.61% higher in plots planted with Larix kaempferi than in those planted with Pinus densiflora. Regarding the dominant phyla, the relative abundance of Ascomycota in heavy rainfall plots was 14.16% and 13.10% higher than in the control and drought plots, respectively, and the relative abundance of Mortierllomycota was 55.48% higher under Larix kaempferi than under Pinus densiflora. The overall results are considered to reflect the microbial sensibility to environmental conditions and interaction with the planted species. Since the current study observed only short-term responses to extreme climate events, further study is required to determine the continuous effects of environmental changes on the associations between plants and soil microbes.